Semiconductor device

Abstract

A semiconductor device, including: a lower phase switching element connected in series with an upper phase switching element; a lower phase power supply which outputs a lower phase side driving voltage; a lower phase drive control circuit which receives the lower phase side driving voltage and drives and controls the lower phase switching element; a bootstrap circuit which receives a charging current from the lower phase power supply, responsive to the lower phase switching element being turned on, and generates a charging voltage therefrom; and an upper phase drive control circuit which receives the charging voltage as an upper phase side driving voltage, which includes a charging current limiting circuit for limiting the charging current flowing from the lower phase power supply to the bootstrap circuit according to a voltage level of the charging voltage, and which drives and controls the upper phase switching element.

What is claimed is: 
     
         1 . A semiconductor device, comprising:
 an upper phase switching element;   a lower phase switching element connected in series with the upper phase switching element;   a lower phase power supply which outputs a lower phase side driving voltage;   a lower phase drive control circuit which receives the lower phase side driving voltage, and drives and controls the lower phase switching element;   a bootstrap circuit which
 receives a charging current from the lower phase power supply, responsive to the lower phase switching element being turned on by the lower phase drive control circuit, and 
 generates a charging voltage therefrom; and 
   an upper phase drive control circuit
 which receives the charging voltage as an upper phase side driving voltage, 
 which includes a charging current limiting circuit for limiting the charging current flowing from the lower phase power supply to the bootstrap circuit according to a voltage level of the charging voltage, 
 and 
 which drives and controls the upper phase switching element. 
   
     
     
         2 . The semiconductor device according to  claim 1 , wherein the charging current limiting circuit is configured to limit the charging current by
 providing a large resistance value when the voltage level of the charging voltage is lower than a predetermined level, and   providing a small resistance value when the voltage level of the charging voltage is higher than or equal to the predetermined level.   
     
     
         3 . The semiconductor device according to  claim 2 , wherein:
 the bootstrap circuit includes a diode and a capacitor;   the charging current received by the bootstrap circuit flows through the diode to the charging current limiting circuit;   the capacitor is configured to be charged by the charging current; and   the charging voltage is generated by electric charges stored on the capacitor.   
     
     
         4 . The semiconductor device according to  claim 3 , wherein:
 the charging current limiting circuit includes:
 a comparator having an inverting input terminal and a non-inverting input terminal, the comparator being configured to output a comparison result by comparing the charging voltage with a threshold voltage at the predetermined level, 
 a first limiting resistor having a first end and a second end, 
 a second limiting resistor connected in parallel with the first limiting resistor, the second limiting resistor having a first end and a second end, and 
 a switch which performs switching according to the comparison result; 
   the lower phase power supply has a positive electrode end and a negative electrode end, an anode of the diode being connected to the positive electrode end;   the capacitor has:
 a first end that is connected to
 the non-inverting input terminal of the comparator, 
 the first end of the first limiting resistor, and 
 the first end of the second limiting resistor; and 
 
 a second end that is connected to the lower phase switching element, so as to be connected to the negative electrode end of the lower phase power supply when the lower phase switching element is turned on; 
   the threshold voltage is applied to the inverting input terminal of the comparator;   the switch has a signal input terminal and a signal output terminal;   the second end of the first limiting resistor is connected to the signal output terminal of the switch and a cathode of the diode, and the second end of the second limiting resistor is connected to the signal input terminal of the switch;   the switch turns off in response to a low potential level signal being outputted from the comparator, so that the charging current limiting circuit provides the large resistance value that is a resistance of the first limiting resistor; and   the switch turns on in response to a high potential level signal being outputted from the comparator, so that the charging current limiting circuit provides the small resistance value, which is a combined resistance of the first limiting resistor and the second limiting resistor connected in parallel.   
     
     
         5 . The semiconductor device according to  claim 4 , wherein
 the charging current flows to generate a first inrush current in response to the switch turning off, and   the first limiting resistor is configured to have a resistance value by which a peak value of the first inrush current is equal to or lower than a rated current value.   
     
     
         6 . The semiconductor device according to  claim 5 , wherein
 the charging current flows to generate a second inrush current in response to the switch turning on, and   the first limiting resistor and the second limiting resistor are so configured that the combined resistance keeps a peak value of the second inrush current to be equal to or lower than the rated current value.   
     
     
         7 . The semiconductor device according to  claim 3 , wherein:
 the charging current limiting circuit includes:
 a comparator having an inverting input terminal and a non-inverting input terminal, the comparator being configured to output a comparison result by comparing the charging voltage with a threshold voltage at the predetermined level, 
 a first limiting resistor having a first end and a second end, 
 a second limiting resistor connected in series with the first limiting resistor, the second limiting resistor having a first end and a second end, and 
 a first switch and a second switch, each of which performs switching according to the comparison result of the comparator, and has a signal input terminal and a signal output terminal; 
   the lower phase power supply has a positive electrode end and a negative electrode end, an anode of the diode being connected to the positive electrode end;   the capacitor has:
 a first end that is connected to
 the non-inverting input terminal of the comparator, 
 the signal input terminal of the first switch, and 
 the signal input terminal of the second switch; and 
 
 a second end that is connected to the lower phase switching element, so as to be connected to the negative electrode end of the lower phase power supply when the lower phase switching element is turned on; 
   the threshold voltage is applied to the inverting input terminal of the comparator;   the first end of the second limiting resistor is connected to the signal output terminal of the first switch, and the second end of the second limiting resistor is connected to the signal output terminal of the second switch and the first end of the first limiting resistor;   the second end of the first limiting resistor is connected to a cathode of the diode;   the first switch turns on and the second switch turns off, in response to a low potential level signal being outputted from the comparator, so that the charging current limiting circuit provides the large resistance value, which is a combined resistance of the first limiting resistor and the second limiting resistor connected in series; and   the first switch turns off and the second switch turns on, in response to a high potential level signal being outputted from the comparator, so that the charging current limiting circuit provides the small resistance value that is a resistance of the first limiting resistor.   
     
     
         8 . The semiconductor device according to  claim 7 , wherein
 the charging current flows to generate a first inrush current, in response to the first switch turning on and the second switch turning off, and   the first limiting resistor and the second limiting resistor are so configured that the combined resistance keeps a peak value of the first inrush current to be equal to or lower than a rated current value.   
     
     
         9 . The semiconductor device according to  claim 8 , wherein
 the charging current flows to generate a second inrush current, in response to the first switch turning off and the second switch turning on, and   the first limiting resistor is configured to have a resistance value by which a peak value of the second inrush current is equal to or lower than the rated current value.